There are many applications for fluid pressure actuated switching arrangements in which the development of a predetermined differential triggers the switching. Internal combustion engines are currently equipped with extensive emission control equipment which often requires the use of electrical switching controlled by engine manifold pressure. Since such pressure is below atmospheric, this is often referred to as engine manifold vacuum.
A typical design for such application consists of a pressure responsive actuator such as a spring-biased diaphragm disposd in a housing, with one side of the diaphragm being exposed to atmospheric pressure and engine manifold pressure applied to the other side, together with a microswitch actuated by movement of the diaphragm in response to the engine mainfold vacuum conditions.
For automotive applications, the cost of manufacture of the device is of paramount importance due to the extremely large volume production required. Thus, the switching action while being extremely reliable, and while also the pressure conditions at which the switching is activated should be able to be set within reasonably close limits, these ends must be met without entailing precision manufacturing processes so as to enable low cost manufacture of the switch.
A general requirement of electrical switching technology is that the contacts should be made and broken rapidly such as to prevent an arcing condition developing at the contacts as they approach or recede from each other.
Such arcing can be prevented by a snap action pressure switch.
Such snap action arrangements which have heretofore been provided have been relatively complex requiring a movable piston or auxiliary contact or spring in executing the snap action motion. Such snap action motion should desirably be highly reliable in operation for the reasons noted and should occur at appropriately closely controlled pressure conditions.
The existence of a hysteresis condition also insures that arcing of the contact will be held to a minimum, i.e., that the snap-over pressure conditions causing movement to either position of the snap action actuator should differ by a significant degree such that a fluttering of the contacts does not occur at the snap-over pressure.
The reliability of the switching arrangements in which there are incorporated fluid actuated elements may be adversely affected, if the movable element carries the electrical lead which is secured thereto and if any significant degree of flexing of the movable element occurs. This is because there is a tendency for strain in the flexing element to disrupt the bond between the electrical lead and the movable element, especially a problem in the switch is required to operate over an extended period of time.
Finally, since such switching arrangements may require either single or double poles, the switching configuration should be such as to be readily adapted to a single or double pole application.
Accordingly, it is an object of the present invention to provide a fluid pressure actuated switching arrangement in which the switching is executed by the actuator device itself to thus eliminate the need for separate switches and to thereby simplify and reduce the costs of the switching arrangement.
It is a further object of the present invention to provide such a fluid pressure actuated switch which is extremely simple in construction and which is easily adapted to either single or double pole configurations.
it is yet another object of the present invention to provide such a switching arrangement which is extremely reliable in operation and which the pressure conditions producing actuation of the switch are adjustable such as to insure accurate control over the actuating pressure conditions.
It is yet another object of the present invention to provide such a switching arrangement in which the movable element actuated by the pressure condition acts as an electrical conductor, but in which the electrical lead is not bonded to the element, such that the flexing movement of the pressure actuated element does not produce a disruption of the electrical connection.